The present invention provides an improved needle-guard assembly for medical devices which are used, for example, in the administration of drugs or for the withdrawal of blood. More particularly, the invention relates to needle-bearing medical appliances, such as hypodermic syringes, i.v. catheter placement units, phlebotomy (blood-collecting) apparatus and the like, furnished with retractable, tubular shields designed to protect the needle portion of such devices prior to use, and to be locked around the needle after use in order to prevent injury from accidental contact.
Needle-bearing devices which are utilized for the subcutaneous or intramuscular injection of medicaments, or for insertion into a blood vessel are generally manufactured in disposable form so as to reduce the risk of patient infection. One group which remains at risk in dealing with such devices are health care professionals and housekeeping personnel who must handle these skin-puncturing devices after they have been used. Contaminated needles present a substantial health hazard and can result in transmission of a number of potentially life-threatening diseases.
That this problem has been recognized in the art is evidenced by the number of patents which have issued directed to apparatus for shielding needles after use, for example, U.S. Pat. Nos. 3,890,971, 4,139,009, 4,507,117 and 4,592,744. Of particular interest to the background of the present invention are three United States patents which employ retractable, tubular shields adapted to surround the needle portion of a disposable hypodermic syringe after it has been used--U.S. Pat. Nos. 4,425,120, 4,573,976 and 4,631,057.
U.S. Pat. No. 4,425,120 (Sampson et al) describes a hypodermic syringe having a tubular shield which is designed to be locked in either a needle-shielding position or a retracted position. The shield is held in either of these two positions by means of upstanding pins on the syringe body which are adapted to cooperate with tracks formed in the shield. Locking is accomplished by rotating the shield so that the pin is held by an offset at the terminus of the track.
A later Sampson et al patent, U.S. Pat. No. 4,573,976, depicts a syringe having a tubular shield equipped with an upstanding catch which is designed to hold the shield in either a needle-covering or a needle-exposed position. The device shown in this patent is said to be an improvement over the apparatus shown in the patentees' earlier U.S. Pat. No. 4,425,120 patent in that locking and unlocking can be accomplished without rotational movement of the shield.
U.S. Pat. No. 4,631,057 illustrates a third injury-preventing adaptation which permits movement of a tubular guard on a syringe body between needle-covering and needle-exposing positions. The guard is held in either of these positions by means of a collar located adjacent the distal end of the syringe barrel. The collar has circumferential indentations which are adapted to cooperate with projections on the interior of the tubular guard. This design permits easy disengagement of the guard from the latched position when the guard is in the retracted (needle-exposed) position. However, when the guard is in the extended (needle-covering) position, the shield is held in a substantially permanent locked condition. Prior to being used to dispense a liquid medication, a separate shield is required to cover the needle.